YankeeDiesel is a research project to design a more efficient engine. It started with “wouldn’t it be nice if” exhaust gases powered the supercharger. This is similar to turbochargers in four-stroke engines but the world’s most efficient engines are two-stroke diesels and they need superchargers. The concept of a traditional engine had to be changed dramatically. The traditional combustion chamber was replaced with reciprocating combustion chamber. A planetary crankshaft to designed to provide that reciprocating motion. And a throttle was added that effectively allows the engine to change size while maintaining a constant compression ratio.
This new engine has no connecting rods, no separate camshaft and no side loads on the cylinder walls. The engine is more efficient because the combustion gases expand a second time. Efficiency is farther improved because the combustion chamber effectively changes size to allow a stoichiometric air/fuel mixture at different power levels. The engine is quieter than traditional engines because the exhaust gases are expelled at lower pressure and over 180 degrees of crank rotation. Details of this invention are in USPTO 8210136. Many configurations were attempted and as the changes became smaller, a successful design has been found. The design evolution of this new engine is shown here.